this is the method my mom showed me when i was little. it's easy and it works! this is for non separating zippers.
first sew the back seam of the dress/garment as if there was no zipper. then zig-zag the edges.
then pin your zipper into place
sew the zipper with the zipper foot, and go back and forth at the bottom of the zipper to re-inforce that area.

and view from the right side
use your seam ripper to open the seam, starting at the bottom
the opened zipper
the closed zipper
i hope this helps! let me know if my instruction are unclear.
erin